Cycloidal rotor for aircraft



Jan. 1, 1952 H. M. HEuvER CYCLOIDAL ROTOR FOR AIRCRAFT 6 Sheets-Sheet 1.

Filed July lO, 1945 Jan. l, 1952 H. M. HEUVER CYCLOIDAL ROTOR FORAIRCRAFT Filed July l0, 1945 6 Sheets-Sheetl 2 INVENTOR. #65567 M #fw/5H. M. HEuvgR cYcLoIDAL Ro'roa FOR AIRCRAFT Jan. 1, 1952 6 Sheets-Sheet 5Filed July l0, 1945 INVENToR. Hf/255er /M #fw/fe BY K Jam 1. 1952 H. M.HEUVER 2,580,428

CYCLOIDAL ROTOR FOR AIRCRAFT Filed July lO, 1945 6 Sheets-Sheet 4 .Y A rf M l l .IIA l) V 757/54 m//// II y. f WVM@ 1. M ,l/ v A Jan. 1, 1952 H.M. HEUVER cYcLoIDAL Ro'roR RoR AIRCRAFT 6 Sheets-Sheet 5 Filed July 10,1945 Jan. 1, 1952 Filed July 1o, 1945 6 Sheets-Sheet 6 BLW Patented Jan.l, 1952 UNITED STATES PATENT OFFICE (Granted under the act of March 3,1883, as amended April 30, 1928; 370 0. G. 757) 4 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes without payment to me of anyroyalty thereon.

This invention relates to aircraft and more particularly to cyclogiroaircraft and cycloidal propellers in which a combination of lift andpropulsion forces are exerted by cycloidal motion of airfoil members orblades cantilevered transversely of the flight path, and constitutes anim- A provement of Patent No. 2,045,233 granted June 23, 1936, to K. F.J. Kirsten andv myself.

Aircraft propellers such as are disclosed in the aforementioned patentand in Patents No. 1,432,-

700 and No. 2,090,052 issued to K. F. J. Kirsten are termed cycloidalpropellers for the reason that the path followed by the longitudinalaxis of any single blade closely approximates a cy- `cloid. Since theblades are rotating about the -r`transverse .propeller axis through theaircraft .and also moving forwardly with the aircraft the -axis of eachof the blades will follow a pure cycloidal curve only ifthe propelleraxis of rotation or orbital axis of the blades advances during onerevolution of the propeller an amount equal to the circumference of thepropeller or pi times the diameter. This translation advance perrevolution of the propeller is termed the pitch, just as the pitch ratioof a screw propeller is defined as the advance per revolution inpropeller diameters 'such a case the pitch or advance per revolution ofthe propeller is considerably more than pi times the diameter of thepropeller. The present invention relates to improvements Vin cycloidalpropellers and particularly cycloidal propellers which are intended tofollow prolate cycloids during normal flight.

. In order to provide a cycloidal propeller capable of sustaining anaircraft and propelling lt forwardly the propeller blades must have anangle of attack with respect to the windstream direction in eachposition of each propeller blade `such that a resultant force isproduced which is capable of furnishing the necessary lift and thrustcomponents required by any `particular, flight ondition. Theserequirements are such that an oscillatory or rotary motion must beimparted to the individual blades so that at each position throughout arevolution of the propeller each blade will furnish its share of liftand. thrust. Of course the aerodynamic considerations of any particularblade will vary constantly throughout a revolution of the propellerbecause of the combined rotary and translatory movement of the propelleras the aircraft is flown.

. In the prior art constructions, such as Patent No. 2,045,233, thechange in pitch or advance per revolution of the propeller has beenaccomplished by an eccentric mechansim which superimposes its effect ona constant velocity drive for rotating the blades about their ownlongitudinal axes. The mechanical difficulties arising from inertiaforces and vibration due to the magnitude of the eccentricity` and largeacceleration in satellite velocity required ovei` certain ranges of theblade cycle have made the attainment of an aircraft capable of slowforward speed impossible and it is accordingly a primary object of theinvention to provide a pitch changing mechanism :for producing thenecessary blade oscillation with a minimum of vibration and to reduce asfar as possible the angular acceleration of the blades in certain rangesof movement about the orbital axis of the blades, so that the instantcenters of the blade axes lie along the mechanical axis of symmetry ofthe propeller at spaced points rather than at a common point as requiredfrom purely geometric pitch considerations.

Other objects and features of my invention will be apparent from thedetailed description which now follows with reference to the appendeddrawings, in which: i

Figs. la, lband lc are vector diagrams of cycloidally moving airfoilsfor the purpose of i1- lustrating the aerodynamic theory of suchdevices; P

Fig. `2 is a side view ofY the exterior of my cycloidal airplane;

Fig. 2a is a plan view thereof;

Fig. 3 is a perspective showing of the rotor structure;

Fig. 4 illustrates details of one of the spindles for supporting a,cantilevered blade;

Fig. 5 is a longitudinal section through one of the mechanisms Aassociated with each rotor;

Fig..5 is aview of a portion of the elements of mechanism A;

Figs. 6a and 6b are diagrammatic illustrations of the mode of operationof my pitch producing mechanism-1 `spective cupsy (Fig. 4). stationaryand is supported in bearings 35a and :mounted by bearing on spindle I5and inte- `grall'y secured to blade 5 by means of a tapering sleeve 23.4lthe same plane and a facing disc21 is secured 1 to theV rims to effecta smooth exterior surface The exterior rims of cups 20 are in for thewhole structure, the discs `21 being ladapted for iiush mounting withlthe fuselage "skin, as will be understood by reference to Figs.

2 and 2a. The tubing structure for the rotor is very rigid and dividesstresses substantially equally among the three tubes forming eachintersection. Each spindle |5 extends a substantial distance into theinterior of its respective blade so as to give considerable cantileversupport through the relatively small bearing '26 (Fig. 4) secured l onthe outer extremity of the spindle by means of a retaining nut 28.

With reference to Figs. 4, 5, 5a and 6a each sprocket wheel 23 isprovided with a sprocket chain 32 which engages a relatively stationary.

sprocket wheel 33 of the same diameter as wheels 23 (Figs. 5a and 6a),there being three such `saine plane as its coacting wheel 33, hence the-wheels 23 do not lie in the same plane but are disposed at differentpoints axially within the re- Shaft 35 is normally 35h in a hollowtubular extension 31 of rotor 2a,

'the extension 31 being operative to rotate rotor propeller 2 and beingrotatively supported in a bearing 31a.. Bearing 31a abuts a flange 31bon shaft 31 and is secured to an apertured cover plate 39. Plate 39 isintegrally secured to a fixed cylindrical housing member 40, and twohousing members 4D are provided, extending between the left and rightrotors of the fore and aft pairs.

Within each housing 40 the tubular extensions 31 (Fig. 5) are suitablycoupled in an integral manner through an intermediate shaft 42 by means`of splines 43 and a threaded collar 45 so that for all practicalpurposes the shafts 31 in each housing are aligned and extend as anintegral member between the left and right rotors of the fore and aftpairs. This laterally continuous construction of the housings 4D andshafts 31 provides a very strong structure for supporting the V fore andaft pairs of propellers and permits the use-of relatively small bearings31a. Rotational power is supplied to the rotors through their respectiveshafts 31 by means of a gear 41 keyed thereto and secured by a nut 41a,and collar 41h which abuts bearing 31a. Gear 41 engages a pin- `ion 4Bwhich is rotated by a shaft 50 supported 'in suitable bearings 50a and50h. Shaft 5l) has pinions 53 are so arranged relative to gears 52 'asto provide contra-rotation of the propeller pairs in the directionsshown in Fig. 2L

The mechanical system including the relatively stationary sprocketwheels 33 at the center of each propeller 2, the sprocket wheels A23secured on the propeller blades 5 andthe continuous drive chains 32connecting respective pairs of sprocket wheels (see Fig. 6a) providesmeans to rotate the blades one revolution for each revolu-` Itl "tion ofthe propeller, the connected wheels 23 and 33 being of equal diameter asnoted ab'ove.

With reference to Figs. 5 and 5a, the mechanism for actuating the bladesis contained with in the expanded cup-like end 34 of shaft 35. Cup 34 isprovided with three slots l60 having midpoints spaced apart and whichare axially separa-ted so that each slot is disposed underneath asprocket wheel 33 as shown. Each midpoint of the slots 6l) diametricallyfaces a lug B2 formed of the material of cup 34 and a lug or tongue 64protrudes through each slot 60 and is secured in a recessed groovemilled in the material of the encompassing sprocket wheel 33, beingsecured thereto in any suitable manner as by screws 66. The lugs 62 andB4 are provided with bores at their extremities and are connected bymeans of similar links 61 and 68, respectively, to the arms a and b,respectively, of levers 1U, there being one such linkage and leversystem associated with each wheel 33. The effective lengths of links 61and 68 are equal, as are the effective lengths of the arms a and b ofthe levers 10. The levers 10 are all rotatably mounted on a commoncantilevered pinor shaft 13 integral with a nut member 14 adapted toride up and down on a screw 15. The pin 13 is guided for translationalmotion by a pin 11 integral with nut 14 and slidably disposed in adiametrical slot 19 milled into a circular cover plate 8l which iss`ecured axiallyto the rotor. A gear train mechanism A' is provided foradjustably setting the pitch of the blades by rotation of the screw 16so as to cause the nut 14 to ride up and down to a predeterminableposition at the will of an operator in a manner to be later described,thereby providing eccentricity of pin 13 relative to the axis of thepropeller, which imparts a crank pin motion to pin 13 and effectsthrough levers 10 and the links Bland 68 a rotational oscillation ofsprocket wheels 33 as the respective propeller revolves. The action ofeach system comprising a lever 1U and related links 61 and 68 is suchthat pin 13 and a pair of imaginary points c and d in i each systemalways remain in approximately a straight line. The point c is normallyiixed with respect to the aircraft and the point d is always fixed withrespect to its respective Sprocket wheel 33. The line defined by thesepoints pivots to and fro about point c in the plane of the paperwhenever` pin 13 is eccentrically displaced and accordingly the levers10 and the related respective links may be regarded as defining straightline mechanisms in the sense that the center of the levers,

i i. e., pin 13, has an approximate straight line mo- `tion with respectto a pair of points c and d in about the axis of its support 34 is afunction of the angular throw of the eccentric pin 13 so thateccentricity required to obtain the necessary sprocket oscillation inlow pitch is reduced as much as one-half which greatly reduces theinertia forces and makes `it possible to attain lower effective rotorpitch settings than can be attained with mechanism known in the priorart.

It will be apparent that if the axis of pin 13 is shifted so as to beconcentric with the rotor and sprocket 33 axis, the sprockets 33 wouldremain stationary and the blades would rotate once around their own axesforeach rotor revolution 7 andthe blades* would remain`V parallel toeach other, correspondingto thecondition of infinite geometric pitch..As the eccentric pin 'i3 is shifted apparent by reference to Fig. 1b,that as the geometric pitch Ais .reduced the oscillation of the bladesmust be increased, which requires that the eccentricity cf pin 13 mustbe increased Yas the pitch is reduced.

The-lever and` linkage structure has the unique effector providing`almost pure cycloidal motion at high pitches, as .will be understoodfrom consideration vof Figs. .5 and a wherein pin 'i3 is shown asaxiallyaligned with-the rotor axis, i. e., no eccentricity is provided, whichcorresponds to a` condition of innite pitch and causes` one completerotation of uniform angular velocity of each blade about its own axiswith respect to the rotor as it traverses the orbit thereof. At infinitepitchthe-acceleration forces in the blades are Zero since with respectlto thel airplane the blades have' no satellite rotation, or in terms ofFigs. la, b and c the center O is at innity; i. e. the blades are alwaysparallel tov each other. However, as

Athe mechanism A' is ,actuated to eiect eccentricity of shaft 73, the'pitch is reduced and acceleration stresses in the blades and in thelinkage and lever structure aswell as in the sprocket wheelV and chainelements are introduced due to the shortening of the radii to themechanical instantaneous center as the pitch is decreased, as

may be seen by comparison of Figs. la and lb.

Also, stresses areY introduced by the fact that at less than infinitepitch the blade must undergo a reversal cfincli-nation, with: respect tothe airplane at two points spaced. 180 apart on the. rotor circle, theprecise points depending on the intersection of the mechanical axis ofsymmetry with the orbit circle. The lower the pitch the greater is theextent of reversal in a given time and hence the greater theacceleration forces; It now be appreciated that ati the high pitchesused in normal cruising these forces are small due to the almost uniformangular Velocity of the" blades. about their own axes, but at lowerpitches, as .at take-off or' in hovering flight, the forces present avserious stress problem. However, the mechanism described above operatesto reduce the peak accelerations but maintains approximately the sameaverage, inl a manner which will be better understood from considerationof Figs. 6c and b and Figs. 7a, b and c in conjunc- ,tion with theexplanation which now follows.

`the 'position shown and the Roman characters I, II and. III denote. thethreeblade systems which V,comprise the propeller, and elements of thesesystems will. be hereinafter referred to accordingly. It.- will be.noted from Fig. 6a thatpthe bladesv II and III-` haveV chords. whichalways: have a com- Vmon: DOint 0f. intersection.with anormal to theYchord of blade' I, the normal being in the plane of thefaxis of thatblade. This relationship is provided for in assembly in a manner tobehereinafter described and it is by virtue of such relationship that achange of pitch changes the blade angles Vin such a manner thatgeometrical symmetry of the three blades always exists so that there isno change in the mechanical `or directional axes of symmetry of thepropeller. In other words, a change of pitch merely varies the point ofintersection of the chords of blades II and III, the point ofintersectionshifting up orvdown on the normal to the chord of blade I asthe pitch is changed, so that the change in angle o-f attack of theblades issymmetrical whereby thepropulsive force of the propeller isaffected only in the direction of the existing night `path as will nowbe made more apparent in discussion of Fig. 6b and Figs. 7a through c.

Fig. 6b shows the blades I, II and III oriented so as to correspond withtheir counterparts in Fig. 6a for the instant shown, although owingtospace limitations on the drawings, blades II and III. are notangularly related to their Vrespective mechanisms in an orbital sense. Amechanical -arrangement is disclosed in each system (Fig. 6b) comprisinga forked lever 80 which is the equivalent of the lever 'IS and therelated link mechanism previously described in connection with Figs. 5and 5a. Each forked member Si! is pivotedY at a point c in litsrespective system, the point c being normally fixed relative to thevaircraft. Each point c corresponds toa point c of Fig. 5a,` the points cbeing similarly spaced 120 apart. A pin d corresponding to any pcintdofFig. 5a is secured to each wheel 33 and eoacts slide-bly with the sidesof the Vslot in the respective member 30. In conformity with theconstruction shown. inY Figs. 5 and 5a the eccentric pin 73 isadjustably positionable along groove 19, pin 'I3 being slidably`disposed pin 'i3 are at alltimes in. approximate alignment,

.the line defined thereby being pivotal. about the respective point cfor each blade system, all as heretofore described. Thus, it will beseen in Fig. 6b that pivots c', d and '13.provide a theoreticalmechanical equivalent of the lever and linkage mechanism in each bladesystem. The

systems I, II and III of Fig. 6b operate insuchV a manner that as thepropeller is rotated coun- .terclockwise` all the blades rotatetherewithv as does the eccentrically disposed pins '13,` the latterrevolving about the propeller axisas indicated by the dot-dash` circleand in Va direction indicated byV an arrow tangent thereto in each sys'-tem. This rotary motion of pin 'i3 produces an oscillatoryVV motion ofeach member B about its respective pivot c', and as in the previous case'(Figs. 5 and 5a) the magnitude of oscillation .depends upon thepredetermined extent r of eccentricity of pin I3 relative to thepropeller axis, the greater themaignitude of oscillation the.. lower vthel pitch? of the propeller.

is now called to systemI inf Fig. 6b which shows Particular attention 9the slot in member so lined up with groove 19 so that the -axis of thegroove andthe slot', as well as pivots c', d and pin 13, are all alignednormal to the chord of the respective blade and intersecting the chordat the transverse axis thereof. In this condition the accelerationforces in the mechanism and in the blade are :at a minimum. Bycomparison with system II (Fig. 6b) it will be seen that the dot-dashline X--X corresponds to the vsame minimum acceleration condition,showing that When pivots c', d' and pin 13 are aligned diametrically theacceleration forces on the respective blades are at a minimum, andsimilarly in system III the line Y-Y indicates the position of themember 80 therein for minimum acceleration. It should be noted, however,that only in system I is the alignment of member 8D normal to the bladechord in minimum acceleration condition. These positions of members 8i)for minimum acceleration are important in that they enable arelationship between the mechanism and the blades to be obtained suchthat a condition of symmetry of the blades is eifected. The symmetricalresult is achieved by rst setting up the relationship shown in system Iso that the pivots c', d' and pin 13 are yaligned normal to the bladewhen the blade is tangent to the orbit circle. For convenientillustration, the position of the axis of blade I will be assumed to beas shown in Fig. 6a although the perpendicular relationship with member80 may be obtained anywhere on the orbit circle and is not limited tothe specific orientation shown on the figures of the drawing. It wil1 benoted that the mechanism of the three systems are interrelated so that,assuming system I has been set up as shown, a 120J counterclockwiserotation of the propeller will automatically bring the axis of member 8Bof system III into coincidence with the line Y-Y whereas a further 120counterclockwise rotation will yautomatically bring the member 80 intocoincidence with the line X--X (note system II). AAccordingly, aftersystem I has been set up, the propeller is rotated 120 counterclockwiseso that the member 80 of system III assumes the position indicated bythe line Y-Y. The' axis of blade III will then be at the point shown forblade I (Fig. 6a) at which time blade III may be oriented by slippingthe respective sprocket chain, or in any other suitable manner, so as tobe tangent to the orbit circle at that point. The blade of system IIIWill then -be in the identical juxtaposition previously had by blade Iwith relation to the orbit circle, which latter blade is now 120 away ina counterclockwise sense, i. e., its axis is now fat the point shown inFig. 6a for blade II. System III having been set up, similarly the bladeof system II is disposed in turn tangent to the orbitcircle afteranother 120 counterclockwise rotation of the propeller at which timemember 80 of system II is in the position of minimum acceleration asindicated by the line X-X and blade II is in the identical juxtapositionshown for blade I in Fig. 6a.V With the blades and their respectivemechanisms set up as just described, a condition of symmetry is obtainedsuch that each blade assumes the position shown in systems I, II and IIIof Fig. Gasuccessively as it revolves about the propeller axis.Furthermore, for any changerin eccentricity of pin'13 only themagnitudeof oscillation is affected, that is at any particular point inthe orbit all of thejblades will be disposed at the same angle relativeto themechanical axis of symmetry. The` foregoing ample for illustrativepurposes.

demonstrates the effect obtained with the structure shown in Figs. 5 and5a wherein an identical method of successively setting the bladestangent to a selected point on the orbit is utilized, the positions ofminimum acceleration of the several lever and link systems beingobtained by instrument measurement or in any other suitable manner, thepoints c, d and pin 'I3 being diametrically aligned in each system atthe time of minimum acceleration therein. i

Attention is now invited to Figs. 7a, 7b and 7c which show vectordiagrams of velocities and forces for a blade of a cycloidal propelleractu-- ated by my novel mechanism. With particular reference to Fig.7a,v a blade, symbolized by the chord thereof, is shown at six stationsabout the orbit circle of a propeller. By comparison with Fig. 1a itwill be noted that my mechanism gives a motion to the blade deviatingsomewhat for pure cycloidal motion for the reason that in Fig. 7a themechanical instantaneous center for stations 2 and 6 is at point O"whereas the mechanical instantaneous center for stations 3 and 5 is atpoint 0'. i

The center for station l Would lie on the mechanical axis of symmetrysomewhat above O", and the center for station 4 would lie somewhat loweron the axis than 0"', but for simplicity these centers have been omittedin Figs. 7a and 7b, since discussion of stations 2, 3, 5 and B is Thiseffect of separating the instantaneous center is due to the nature ofthe mechanism comprising the lever 1U and the related links (Figs. 5,5a) in each blade system and the equivalent mechanism of Fig. 6b

would likewise produce the same effect. It will be noted, by comparisonwith Fig. 1a, that the instantaneous radii of mechanical rotation atstations 2 and 6 have been shortened whereas the corresponding radii atstations 3 and 5 have been lengthened `A novel result is therebyobtained, namely, the acceleration forces required to oscillate theblade and the acceleration stresses in the blade itself are increased atstations 2 and 6 but .decreased'at stations 3 and 5, as will be evidentfromk consideration ofthe kinematics of Fig. 7a. Further, since themechanical center for stations 2 and 6 has been moved up- Wardly, thechord angle of the blade with respect to the horizontal at stations 2and 6 is decreased whereas the mechanical center of the blade atstations 3 and 5, having moved downwardly, the chord `angle isincreased. The resultant force on the propeller as a Whole, however, aslderived from the forces shown at the several stations, is such that thesummation of lifts is equal to zero, whereas the summation of thrusts isforward for the velocities shown. It should be noted, however, that theinstantaneous directional center O has remained substantially unaffectedby the displacement or splitting of the mechanical in- Attention is nowcalled to stantaneous centers. Fig. 7b which differs from Fig. 7a inthat the pitch has been increased to an extent such that the mechanicalinstantaneous center O" for the blade at stations 2` and 6 and themechanical instantaneous center 0" for` the blade Iat stations 3 and 5has been further displaced along the mechanical axis of symmetry. In thecondition shown in Fig. 7b, the radiito al1 stations have been increasedas compared with Fig. 7a, but itwill be notedthat at the reduced pitchin Fig. 7a the ratio of the length of the radii to stations 3 and 5 withrespect to the corresponding radii in Fig. 7b is larger than the ratioof the radii l1 to stations .2 and .6. of Fis. 7o with' -respeet toy.the eereeeondineiadii of'Fis 71h.-

otlier Weeda' my .meohanism effeets a eotnoreinise in radii between thestations in the lower part of theorbit circle in comparison with thestations the upper part of the orbit circle such that as the Chordansie, is ieolneed,` the aeeeleratien iorees arev inversely affeeted;th; t is. the aeeeleratien foreesat-the lowerstatons arehot teased asmuch as are the forces at theupper Vations. Aceordinsly. Sinee thestrutture .has inherently lower stresses at the doper stations dde tothe longer radiithereto, this feature. eneots a eomoromise in thelaanortionnnent of stresses which is ad- Y Vantaseods in the oraetie-aioperation of the meehanisin and the blades The-summation ofr feiees ,Iland T- is sraphieally shown on Fis. 7b dhd it will be noted, that'the.Change pitch has not, affected the lift hashes increased the thrust inthe .direction of night similar to the-enact. found -for pureeycloida-l'motion as shown onl Fig. la In other Words, the-mechanicaland dii'ee-r tionalaxes of symmetry being coincident for both Figs. 7aand 7b, only the magnitude-of oscillation or the blades has'beenaffected by the change Yn Pitch and it may now he noted by comparison oithese two sures that the blades, if extended at stations 2 and-li (orand'e). would intersect en the normal tothe blade at station I. hereetofore stated in tile discussion of ne. ea. With reference toFig. 7c, itwill be seen that the meehahieal anis of symmetry .has been shifted in amanner corresponding to Eig. lc, Thus the phase oi-oseillatioiioitheblade has `been changed with teeheet to the several stations shown onthe rotor circle and due to the peculiar nature of mechanism eachstation now has an instantaneous mechanical center which fallssubstantialli7 on the theehanioal oi symmetry and which. are. indicatedas VO1 through Qs .to eorreepend with the siibseriot neta-tion oi theseveral stations. Here again, it will heheted that stations, 3. ll land5`Y the lower half of the rotor circle have instantaneous VCenterswhich.,V though separated. are in each case lower than'the instantaneouscenters for stations I, 2 and 6, thereby preservine the Compromiseeieet4 insofar as aeeeletation stresses kare concerned.V The amount ofangular displacement'of the mechanica1 axis'ofsymmetry from'thedirectional axis ofsyrnmet ryv in the easev oi Fisla an extremeCondition, and ref s ults in anegative thrust `for summation Tandconsiderata,le` positive lift in conformity with the effect achievedfor'the magnitude and phase conditions `of Fig. le; that is, theaircraft, ifuncler propulsive power, would be retarded, but if beingtowed as a 'glider' would experience auto-rotation of the blades.

It will be apparent from the preceding descrip-f., tion and withparticular'referenceto Figs. 7a, 7band 7c that the changes in pitchsetting forfthe rotor are primarily related only to variations inIthrust and that the, lift'obtained would be small; in magnitude, sothat a rotor 'of the kind dee scribed if provided with only a pitchchange mechanism would be suitable only as .a propulsion means and someadditional sustention means, would be necessary for the aircraft. Byinspection of Fig. 7c however, it is dapparen t that byehanse in thephase ansie of the blade oseillation or shift in the mechanical axisoffvsymmetry the, resultant force can be' chgnigedin'direction so. thatit has a very large lift component and a Zero or reverse thrust.eoinponent- Brehansiiis the, eitohesett. s of -theiotors st.

forward speed.- and-h shift the mechanical anis-oi symmetry the thrustcan he converted to a lift of any desired .magnitude so that the craftmay be .Caused to descend. remain in level flight, or climb. Bydifferentially changing the pitch of the Pairs of rotors on oppositesides of the aircraft, yawing moments are created about the center ofgravity to cause turning land differential shifting-ofv the mechanicalaxes of sym.,- metry between pairs of rotors on opposite sides of theaircraft and thus produce roll of the aire craft, while a diierentialchange between fore and aft pairs of rotors produce pitching moments enthe-aircraft; Therneehanisms for obtaining pitch change, for shiftingthe mechanical axis of symmetryiand the control vsystem for shifting`the` mechanical axiseot piteh of the rotors will now be described,

The mechanism A' (Fig. V5? lelfects pitch adjustment by. actuation of apair of bevel gears 35 and 8 6, the gear 85 Abeing integra-l with thescrew "76.

and the gearl 86 being keyed to a shaft S9 having a pinion-9| keyed atthel other end thereof and engaging the teeth of an internal gear 93rotatably secured axially to the rotor by a ring 95 bolted to the rotor.Normally gear` 93 rotates with the rotor and there is no relative motionbetween pinion 9! and gear 93. Ensuring rotal tion .of gear 93 with therotor is :a compound Vgear 91 rotatively mounted on a shaft 98 but notkeyed. thereto. The larger gear of. gear Sl' engages gear 93 but has noconnection with pinion 9i exceptV by virtue of their. individualengagement with` rotatably secured on aV disc-like member I3= whichintegral with the shaft 93. Rotatablyi mounted on shaft 98 is acup-shaped gear |96,- provided with internal and external teeth, theinternal teeth being. adapted to engage theplane-Y tary pinions IBD andIllI and the external teeth being. adapted to engage the teeth of a gearItl9l which may, as shown, be milled outy of the material of shaft 3l.Shaft 98 has keyed thereto a4 bevel gear I I2 provided in a; housingformed in' thelplate 39 and a bevel pinion II3 journalled in plate'39 isprovidedand adapted for manual ro,- tatiomso as to. rotate gear H2 andshaft 98;

The. arrangement is such that rotation of the' rotor. by vir-tue offrotation of shaft 3.1 effects throughgear |09 a rotation of gear'l whichis rotatable.only about its own |axis and which, in o turn, causesrotation of pinions |99 and IUI about their own axes, thereby rotatinggear 9'.' which is journalled on vshaft 98, which in turn causesrotation of gear 93; The. ratios provided among.

the several rgears 93.-I99 is such that the larger gear of compound`gear 9.1 causes rotation of gear: 9 3 at the. sarneiR. P. VM; as the.rotor. However,

when shaft; 9,8 iS,Y rotated by virtue of. the bevel gearv combination`II2 and II3, at. the will of theV operator, planetary pinions I Ill)``and II are rerotation/ of gear 91 which nowA rotates gear93. fasten orslower than the rotor, depending.' on the direction of revolution ofpinions |00 and. wl about; shaft 9:8.. 5 9e; acting trl-mighpimon si,shaftr sa, gewaar@ volved-aboutthe axisof the shaft; 98 and effect Thisrelative rotation of' gear-'- lf3 rangement 85 and 86 and screw 16serves `to translate nut 14 Aeccentrically of the axis of the rotor toladjust the pitch of the blades by effecting eccentricity of pin 13 ashas heretofore been described.

It will be understood that eccentricity of pin 13 will ordinarily beprovided in one direction only with respect to the propeller axis, dueregard being had for the initial disposition of the mechanical axis ofsymmetry of the blades, so as to effect only forward thrust. Undercertain conditions the ship could be made to fly backwards were pin 13rendered eccentric on the opposite side of the propeller axis, but ananalysis of this phenomenon is not thought necessary to a satisfactorydisclosure of my invention.

rIfhe means for varying the mechanical axis of symmetry is' themechanism A as shown ln Figs. 5 and 8, which comprises a gear I |1milled on the end of shaft 35 and engaging the smaller gear of acompound gear |20 which is rotatably supported on :a shaft |22 suitablysecured as by straps |24 tand |25 on the shaft 31. The larger gear ofcompound gear |20 engages the smaller gear` of another compound gearl|28 rotatably secured in a similar mannerv on shaft 31, as shown onlyin Fig. 8. The larger gear of compound gear E28 is disposed forengagement with teeth provided internally of a worm gear |3|, theexterior of which is provided with worm teeth adapted to engage amanually operable worm |34. Gear |3| and worm |34 are rotatably mountedwithin the stationary housing 40 in any suitable manner. For example,gear |3| could be journalled on shoulders |31 provided peripherallythereof, while worm |34 could be journalled at its ends in suitablebearings (not shown). As shaft 31 rotates with the rotor and gears |2and |28 revolve therewith about the rotor axis, by virtue of theengagement ofthe larger gear of gear |28 with the internal teeth of thenormally stationary worm gear |3|, gear |28 is caused to rotate aboutits own axis which, in turn, causes rotation of gear |20 about its ownaxis. However, the ratios provided between the several gears is suchthat the rotation of the smaller gear of gear |20 about its own axis hasa tangential velocity equal to and in an opposite direction with respectto the tangential Vvelocity of revolution of gear |20 about the rotoraxis. Accordingly, with gear |3| normally stationary, gear |20 rotatesabout its own axis and` revolves about gear |l1 thereby holding shaft 35stationary relative to housing 48. When, however, worm 34 is manuallyoperated thereby causing rotation of gear |3| and effecting rotation ofgear |28, the rate of rotation of gear |20 is changed, i. e., it isincreased orv decreased depending on the direction of rotation of worm|34, thus causing rotation of gear l1 which compels rotation of shaft 35in a direction depending upon the direction of rotation of worm |34 andto a proportional extent. Rotation of shaft 35 effects rotation of theintegral lugs 62 which actuate their respective links and levers 10 toorient lugs 64 whereby sprockets 33 are angularly 14 peller todirectlonally control the forces thereon, as demonstratedl in Fig. 7c.It should be noted, with reference to Fig. 6b, that the pivots c',although shown as fixed to ground, i. e., xed with respect to theaircraft could be arranged to be angularly positionable about thepropeller laxis whereby the mechanical axis of symmetry of the propellercould be varied.

In the complete oycloidal airplane manual operating means should beprovided for actuation of the respective bevel pinions ||3 (Fig. 5) sothat equal or differential adjustment as between the left and rightrotors is obtainable. Also manual operating means should be provided foractuation of the respective worms |34 in the control mechanisms A", sothat the mechanical axis of symmetry of the four propellers may bevaried jointly or differentially.. t j

From the above description it will be appreciated that I have provided acycloidal airplaneA and control system therefor, whereby manual controlsin the airplane can effect complete control of the airplane byadjustment of the several rotors or propellers. It should be understoodthat the airplane is not limited to the exact number of rotors shown andthat any multiple of four rotors could ,be used to obtain the controleffects in the mannerl taught herein without departing from'the spiritof the invention.

The term pitch as used in the foregoing discussion of the operation ofthe rotors and airplane is only the theoretical pitch as it isinfluenced by the relative setting of the rotor blades and theirrelative motion during 'a particular cycle of operation. The actualrotor pitch in an airplane built in accordance with the principlesoutlined herein will depend on numerous additional factors, such as thecross sectional shape of the rotor blades, the number of blades perrotor, the diameter of the rotor in relation to the blade chord, thenumber and relative disposition of the rotors on each side of theairplane, the magnitude and direction of winds and the forward speed ofthe airplane with respect to the surrounding air. All theseconsiderations will influence `the actual pitch of the rotors as well asthe` instantaneous `center of rotation of each rotor but` theseconsiderations are varia-bles only determinable by design, accuracy ofconstruction and operating conditions.

Although many of the structural details of my invention have beenomitted for the sake of more clearly emphasizing'that structure which Iregard as novel, it will be understood that such details may readily besupplied by persons skilled inthe art and that the invention asdisclosed represents thebasic structure for purposes of illustration,and I seek patent protection therefor Within the scope of the Yclaimsappended hereto.

I claim:

1. A cycloidal propeller for aircraft comprising, aY rotatably mountedrotor having a plurality of blades extendingv therefrom in generallyparallel relation and rotatable with said rotor, means mounting each ofsaid blades for rotation about its longitudinal axis relative to saidrotor, a control mechanism for regulating the rotative positions of saidblades with respect to said rotor including first sprocket memberscoaxial of said blades and second sprocket members coaxial of said rotorand said first sprocket members being fixed on the respective blades,independent chain drive means connecting the respective first and secondsprocket members, a pin near the axis of rotation of said rotor landrotatable with said

